Most persons with type 2 diabetes are overweight, and obesity worsens the metabolic and physiologic abnormalities associated with diabetes. Our objective was to assess the effectiveness of lifestyle and behavioral weight loss and weight control interventions in adults with type 2 diabetes. Studies were obtained from searches of multiple electronic bibliographic databases, supplemented with hand searches of selected journals and consultation with experts in obesity research. Studies were included if they were published or unpublished randomized controlled trials in any language that examined weight loss or weight control strategies using one or more dietary, physical activity, or behavioral interventions, with a follow-up interval of at least 12 months. Effects were combined using a random-effects model. The 22 studies of weight loss interventions identified yielded a total of 4659 participants with a follow-up of 1 to 5 years. The pooled weight loss for any intervention in comparison with usual care among 585 subjects was 1.7 kg (95% confidence interval [CI]: 0.3 to 3.2 kg), or 3.1% of baseline body weight among 511 subjects. Among 126 persons who underwent a physical activity and behavioral intervention, those who also received a very low-calorie diet lost 3.0 kg (95% CI: -0.5 to 6.4 kg), or 1.6% of baseline body weight, more than persons who received a low-calorie diet. Among 53 persons who received identical dietary and behavioral interventions, those who received a more intense physical activity intervention lost 3.9 kg (95% CI: -1.9 to 9.7 kg), or 3.6% of baseline body weight, more than those who received a less intense or no physical activity intervention. Comparison groups often achieved substantial weight loss (up to 10.0 kg), minimizing between-group differences. Changes in glycated hemoglobin level generally corresponded to changes in weight and were not substantial when between-group differences were examined. Weight loss strategies involving dietary, physical activity, or behavioral interventions were associated with small between-group improvements in weight. These results were minimized by weight loss in the comparison group, however, and examination of individual study arms revealed that multicomponent interventions, including very low-calorie diets or low-calorie diets, may hold promise for achieving weight loss in adults with type 2 diabetes.
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